Power plant cycle



Feb. 15, 1966 E. A. PIRSH ETAL 3,234,735

POWER PLANT CYCLE Filed April 10, 1964 2 Sheets-Sheet 1 INVENTORS Edwarq A. Plrsh BY Warme L. SagQ ATTORNEY POWER PLANT CYCLE 2 Sheets-Sheet 2 Filed April 10, 1964 FIG.2

United States Patent Ofiice 3,234,735 Patented Feb. 15, 1966 3,234,735 POWER PLANT CYCLE Edward A. Pirsh, Akron, and Warnie L. Sage, Louisville, Ohio, assignors to The Babcock & Wilcox Company, New York, N.Y., a corporation of New Jersey Filed Apr. 10, 1964, Ser. No. 358,796 Claims. (Cl. 60-39.18)

The present invention relates to power plant cycles combining a steam turbine plant and a gas turbine plant, and especially those of the type which utilize coal or other particulate solid fuel as the single fuel source.

, Presently known combined cycles incorporate a gas turbine plant and a steam turbine plant which utilize oil or fuel gas and coal, respectively, as the fuel source, the gas turbine being in some instances employed as a socalled topping unit to increase the overall thermal efliciency of the cycle. Quite differently, however, the present invention is directed to a combined cycle wherein the gas turbine plant and the steam turbine plant both utilize only a single solid fuel, preferably coal, in the interest of economy.

Coal is frequently used in steam turbine plants to economically generate steam. The steam is used as a motive fluid for driving the steam turbine. However, in gas turbine plants, fuel is burned in a combustor and the gaseous combustion products are then expanded through the gas turbine. When coal is burned in the combustor of a gas turbine plant, special problems arise because the ash and other solids entrained in the products of combustion, here serving as the motive fluid for the gas turbine, are known to cause rapid erosion and deterioration of the working surfaces of the gas turbine, such as the blades or buckets. Hence, it is the principal concern of the present invention to provide an arrangement for a combined cycle plant of the type set forth, which advantageously utilizes coal, or other particulate hydrocarbon fuel as the single source of fuel for the gas utilizing apparatus as well as for the steam utilizing apparatus. This provision necessarily involves the production and refining of combustible gas for use in driving the gas turbine from the same kind of solid fuel utilized for generating steam.

According to the present invention, relating to a combined steam-gas turbine cycle, there is provided first and second steam generator units, a steam turbine or other steam utilizing apparatus, a steam condensing unit, and means for circulating a vaporizable motive fluid through the aforesaid units. In one embodiment of the invention, the fluid is circulated through the units in the order named; and, in another embodiment of the invention, the fluid travels in parallel flow paths through the steam generators before passing through the steam turbine unit and the condenser unit.

Further provided is a gas turbine arranged to receive expansible combustion products from a gas combustor. The gas turbine drives an air compressor which discharges air at superatmospheric pressure for use in the combustor and in the steam generators.

In the present arrangement, a gasifier provides the heat source for the one steam generator under conditions favorable for the production of hydrocarbons of the CnHn series, carbon monoxide and hydrogen, thereby yielding a combustible make-gas. The fuel introduced into the lower portion of the gasifier is burned at near stoichiometric conditions, the gaseous products so produced then reacting with fresh particulate fuel which is introduced into another region of the gasifier.

The walls of the gasifier-steam generator are preferably lined with water cooling tubes in heat exchange relationship with the stream of product gases, steam being generated thereby. If desired, superheating heat transfer surfaces may also be provided. In any case, the steam generated may be made available for delivery to the steam turbine to produce useful work, e.g., convert-.

ing mechanical energy into electrical energy.

The quality of the make-gas is improved prior to its introduction into the combustor by cleaning apparatus which separates the entrained fly coke and ash therefrom. The separated solids are used either as the only fuel or as a supplemental fuel source in the second steam generator, while the improved make-gas is admitted to the combustor where it is burned, yielding substantially ash-free flue gas, which is employed to drive the gas turbine. steam generator, in heat exchange relationship with a suitably disposed heat-absorbing surface, provide the heat source for the generation of steam, which may be superheated if desired, the steam being delivered to a steam turbine. The flue gas, upon leaving the second steam generator, passes through a gas cleaner, from whence these gases and those from the combustor are delivered to the gas turbine.

It is a significant feature of the present invention that the second steam generator utilizes as fuel the particulate matter separated from the make-gas, and that it and its associated cleaning apparatus effectively remove both the ash and alkali-ash compounds from the gas so that it Will be of such improved quality as to be advantageously delivered for use as motive power for the gas turbine.

The various objects, features and advantages of the invention will appear more fully from the detailed description which follows, taken in connection with the accompanying drawings, forming a part of the present ap plication and in which:

FIG. 1 is a diagrammatic illustration of one arrangement of apparatus for carrying out the invention; and

FIG. 2 is an illustration similar to FIG. 1, showing a modified arrangement of apparatus for carrying out the invention.

Since one figure of the drawings illustrates an arrangement of power plant apparatus which is merely a modification of the arrangement shown in the other figure, like reference numerals are employed to designate corresponding parts or components which are of similar construction and which have similar functions.

As mentioned previously, the present invention is applied to combined cycle steam and gas power plants wherein an arrangement is provided for gasifying coal, generating a product gas and refining it to such quality as to make it acceptable for driving the gas turbine, thus utilizing the same solid fuel source as is used for generating and superheating motive steam for driving the steam turbine.

According to the invention, as shown in FIG. 1, there is provided a steam turbine 10, mounted on a shaft 11, in driving relation to an electric generator 12. The steam turbine 10 is driven by a motive fluid, preferably high pressure, high temperature steam, which is received through steam line 13 at the turbine inlet, expanded through the turbine 10, and then condensed into liquid by a condenser 14. The condensation of steam at the low pressure or exhaust end of the steam turbine 10 creates there a vacuum which promotes the flow and expansion of steam through the turbine 10.

The condensate is moved by suitable recirculating means, such as a feedwater pump 16, first through feed line 21 to a condensate-flue gas heat exchanger or economizer 20, next through feed line 21a and on through a tubular heat exchanger 22 of a gasifier-steam generator 24, then through connecting line 25 and on through a tubular heat exchanger 26 of a second steam generator 28 from whence the motive fluid is supplied via steam The products of combustion within the second a line 13 to the inlet of the steam turbine as superheated steam. It is the function of the economizer to preheat the condensate. The surfaces of heat exchangers 22 and 26 serve to generate steam and preferably may superheat it for use in the steam turbine 10.

Further provided is a gas turbine 30 which is mounted on a shaft 31 in driving relation to a second electric generator 32 and to an air compressor 34 which may be of the axial-flow type. In operative association with the gas turbine 30 is a combustor 36 which burns combustible gas and delivers the products thereof through conduit 38 to the inlet of the gas turbine 30 for expansion therethrough. Thereafter, the expanded gas is exhausted from the gas turbine 30, passing via flue 38a and through economizer 20, in indirect heat transfer relationship with the feed water and is then discharged through flue 18 to a stack (not shown).

The air compressor 34 admits atmospheric air to the inlet thereof for pressurization to superatmospheric level, after which it enters discharge duct 35, and from there is conducted to the combustor 36, and also to the gasifier-steam generator 24 and the parallel steam generator 28 by means of respective air supply ducts 37a, 37b, and 37c.

The gasifier-steam generator 24 is preferably of the air-blown suspension type in which vortex-firing is used and ash is removed in the form of molten slag through a slag tap 39 in the gasifier floor. It is the function of the gasifier portion of the gasifier-steam generator 24 to produce so-called make-gas which may consist of such combustible gases as H CO, CH To this end, finely ground aerated solid fuel, such as pulverized coal, is introduced through fuel line 40 into the lower or first region of the gasifier for admixture with the air received through duct 37b from compressor 34. The finely ground fuel particles are there substantially completely burned, yielding high temperature combustion products. Additionally, pulverized coal or crushed coal is fed by another fuel supply line 41 into the gasifier reaction zone so as to come into contact with the high temperature combustion products issuing from the first region under con ditions favorable to the production of carbon monoxide, and hydrogen, and possibly hydrocarbons of the CnHn series, hereinafter referred to as make-gas.

The make-gas yielded as aforesaid in the reaction zone of the gasifier-steam generator 24 is unsuited for combustion as is, if destined for expansion in a gas turbine, because of entrained carbonaceous material, ash and alkaline substances which would erode and corrode critical parts of the gas turbine. In order to overcome these difliculties, the arrangement of the present invention seeks to improve the quality of the make-gas by removing from it the fly coke, ash, and alkali, advantageously disposing of these products in the steam generator 28.

As regards the gas clean-up, low quality make-gas from the gasifier-steam generator 24 is conveyed by line 42 to a'make-gas cleaner 43 which separates out the entrained fly coke, alkali and ash and delivers these products through line 44 to the second steam generator 28 for use as a fuel. Supplementary pulverized coal or other fuel may also be supplied by fuel supply line 45. The upgraded make-gas is passed through conduit 46 to the comustor 36 where it is ignited and burned, yielding hot flue gas. The latter is conveyed by the conduit 38 to the inlet of gas turbine 30.

The complete burning of separated fly coke and other combustibles in the second steam generator 28 also yields high temperature flue gas, but it contains particles of fly ash and residual alkali. These products of combustion exit and pass through line 47. to a high temperature gas cleaner 48, which disposes of residual solids through outlet 49, exhausting clean flue gas through line 50 into conduit 38 where it supplements the flue gas from the combustor 36 travelling toward the inlet of gas turbine 30.

From the foregoing, it will be appreciated that the cleaning, conditioning and upgrading of the make-gas provides separated fines which are used as fuel in the second steam generator 28. The slag from steam generator 28 is discharged through sag tap 51. The cleaned combustion products of the second steam generator 28, together with the combustion products from the combustor 36, provide a most satisfactory gas for use as a motive fluid in the gas turbine.

The tubes of heat exchangers 22 and 26 of the FIG. 1 embodiment are serially arranged in association with their respective steam generators 24 and 28 and are in indirect heat transfer relationship with the hot gases flowing therethrough, each to the end of converting the liquid condensate into steam and superheating the same for driving the steam turbine 10. Thus, a portion of the heat employed and/or yielded in the process of gasification is efficiently utilized in the process of steam generation.

Modification In the modified form of the invention shown in FIG. 2, the tubes of heat exchangers 22 and 26 providing heatabsorbing surfaces are connected in parallel, rather than in series. As shown, feed lines 21b and 55 are connected to the respective heat-absorbing surfaces 22 and 26; and the latter are, in turn, connected to respective steam lines 57 and 13 leading to a common junction point 57a adjacent the inlet of steam turbine 10. Thus, the condensed fluid from condenser 14 may be pumped by condensate feed pump 16 first through economizer 20 and then apportioned to the above-described parallel flow circuits. In other words, one portion of the fluid is conducted through feed line 21a, heat exchanger 22, and line 57 to the junction point 57a; and a second portion is conducted through branch feed line 55, heat exchanger 26 and line 13 to the junction 57a, the combined flow then entering steam turbine 1!).

Feed lines 21a and 55 are each provided with respective adjustable flow-regulating valves 59 and 61 in the parallel flow circuits beyond the junction in line 21a. This provision permits the regulation or stoppage of fluid flow through either or both of the heat exchangers 22 and 26 by the appropriate adjustment of valves 59 and 61; and, of course, with valves 59 and 61 fully opened, each of the parallel circuits will be receiving its fluid through the heat exchangers 22 and 26, respectively.

It is a feature of the FIG. 2 embodiment of the present invention that the gasifier-steam generator 24 and the steam generator 28, with their associated heat-absorbing surfaces of heat exchangers 22 and 26, are operable more or less independently of one another insofar as the generation and superheating of steam is concerned. Therefore, the flexibility of operation of the FIG. 2 embodiment lends itself well to use of the gasifier-steam generator 24 at capacity, while at the same time the steam generator 28 may be operated as desired or required to provide additional steam to meet the steam load demand of the steam turbine 10. This necessarily involves adjusta'bly controlling the amount of fluid supplied to the steam generator 28, and also the appropriate regulation of supplementary fuel input thereto as necessary.

Otherwise, however, the parts and components of the FIG. 2 arrangement designated by like reference numerals are structurally and functionally representative of corresponding parts and components of the FIG. 1 arrangement.

Although the invention has been shown in but two forms it will be obvious to those skilled in the art that it is not so limited, but that it is susceptible of various changes and modifications without departing from the contemplated scope thereof.

What is claimed is:

1. The combination of first and second steam generators, means for delivering a vaporizable fluid to said steam generators; said first steam generator being adapted to burn fuel therein so as to generate combustible makegas products and also to heat said fluid; a first gas cleaning unit connected to said first steam generator so as to receive said make-gas, said first cleaning unit having means for separating entrained solid particles from said make-gas and means for conducting said particles to said second steam generator; said second steam generator being adapted to burn the particles delivered thereto from said first cleaning unit and having means for transferring heat tom the resultant flue gas to said fluid; a second gas cleaning unit having inlet means connected to said second steam generator for receiving flue gas and having means for separating out solid particles from said flue gas; steam utilizing apparatus and means for conveying steam thereto from said steam generators; gas utilizing apparatus, means for conveying cleansed flue gas thereto from said second cleaning unit, a combustion chamber, means for conveying cleansed makegas thereto from said first cleaning unit, and means for conveying gas from said combustion chamber to said gas utilizing apparatus.

2. A power plant comprising: first and second steam generators, a steam turbine unit operatively associated with said steam generators; a gas turbine, a gas combustor operatively associated with said gas turbine; said first steam generator being adapted to burn fuel therein so as to generate combustible make-gas products; a first cleaning unit adapted to receive said make-gas from said first steam generator for separating out entrained solid fuel particles from said make-gas and having means for discharging the cleansed make-gas to said combustor; said sec-ond steam generator being adapted to receive and burn the particles separated 'by said first cleaning unit; and a second cleaning unit connected to said second steam generator having means for separating out solid particles from said flue gas and means for delivering the cleansed flue gas to said gas turbine without going through said com-bustion chamber.

3. A power plant comprising; first and second steam generators, a steam turbine, and means for circulating a vaporizable motive fluid through at least one of said steam generators and said steam turbine; a gas turbine, a gas combustor adapted to discharge its flue gas products of combustion to said gas turbine; said first steam generator being adapted to burn fuel therein so as to generate combustible make-gas products; first and second cleaning units, said first cleaning unit being connected to said first steam generator so as to receive said make-gas, said first cleaning unit having means for separating entrained solid fuel particles from said make-gas and delivering them to said second steam generator, said first cleaning unit further including a discharge line connected to said combustor for discharging the cleansed make-gas thereto; said second steam generator being adapted to burn the particles delivered thereto from said first cleaning unit and discharging the resultant flue gas to said second cleaning unit; said second cleaning unit having means for separating out solid particles from said flue gas and means for exhausting the cleansed flue gas to said gas turbine.

4. Power plant apparatus comprising: first and second steam generators, a steam turbine, and means for circulating a vaporizable motive fluid through said steam generators and said steam turbine; a gas turbine and a gas combustor arranged to discharge its flue gas products of combustion to said gas turbine; means for delivering solid fuel to one region of said first steam generator so as to be burned therein and to another region of said reaction zone so as to be contacted by the hot products of combustion from said one region whereby combustible make-gas products are generated; a first cleaning unit arranged to receive make-gas from said first steam generator and having means for separating entrained solid fuel particles from said make-gas, means for delivering said particles to said second steam gen- 6 erator, and means for discharging the remaining makegas to said combustor; said second steam generator being adapted to burn the solid fuel particles delivered thereto; and a second cleaning unit adapted to receive the flue gas from said second steam generator and having means for separating out and discharging entrained solid particles and means for conducting said flue gas next to said gas turbine.

5. The combination of a steam utilizing unit, first and second steam generators and means for delivering a vaporizable fluid to said steam generators; a gas utilizing unit; said steam generators each having a reaction zone, means for delivering solid fuel to one region of the reaction zone of said first steam generator so as to be burned therein and to another region of said reaction zone so as to be contacted by the hot products of combustion from said one region whereby combustible makegas products are generated and fluid is heated by said hot products of combustion; a first cleaning unit connected to said first steam generator to receive said makegas and including means for separating entrained solid fuel particles from said make-gas, means for delivering said fuel particles to the reaction zone of said second steam generator for burning whereby flue gas is produced, and means for discharging the cleansed makegas to said gas utilizing unit; said second steam generator having means for transferring heat from its reaction zone to said fluid; a second cleaning unit adapted to receive the flue gas from said second steam generator and including means for separating out and discharging entrained solid particles, means for conveying cleansed flue gas from said second cleaning unit to said gas utilizing unit; and means for conveying said fluid from said first and second steam generators to said steam utilizing unit.

6. A power plant comprising: a steam turbine unit, first and second steam generators each having respective first and second heat exchanger units, and means for circulating a vaporizable motive fluid through said units in the order named; a gas turbine, and a gas combustor arranged to discharge its products of combustion to said gas turbine; said first steam generator being adapted to burn fuel therein so as to generate combustible makegas products and also to heat said first heat exchanger unit with its hot products of combustion; a first cleaning unit connected to said first steam generator so as to receive said make-gas, said first cleaning unit having means for separating entrained solid fuel particles from said make-gas and delivering them to said second steam generator, said first cleaning unit further including a discharge line connected to said combustor for discharging the cleansed make-gas thereto; said second steam generator burning the particles delivered thereto from said first cleaning unit and passing the resultant flue gas into contact with said second heat exchanger; a second cleaning unit connected to said second steam generator for separating out solid. particles from said flue gas and exhausting the cleansed flue gas to said gas turbine.

-7. Power plant apparatus comp-rising: a steam turbine unit, a condenser unit, first and second steam generators having respective first and second heat exchanger units in operative association therewith, and means for circulating a vaporizable motive fluid through said units in the order named; a gas turbine and a gas combustor arranged to discharge its products of combustion to said gas turbine; means for delivering solid fuel to one region of said first steam generator so as to be burned therein and to another region of said reaction zone so as to be contacted by the hot products of combustion from said one region whereby combustible make-gas products are generated; said first heat exchanger unit being heated by the hot products of combustion of said first steam generator; a first cleaning unit arranged to receive makegas from said first steam generator for separating entrained solid fuel particles from said make-gas and delivering them to said second steam generator after which the remaining make-gas is discharged to said combustor; said second steam generator burning the solid fuel particles delivered thereto and passing the resultant flue gas into contact with said second heat exchanger; a second cleaning unit arranged to receive the flue gas from said second steam generator for separating out and dischraging entrained solid particles, after which said flue gas is exhausted to said gas turbine.

8. Power plant apparatus comprising: a steam turbine unit, a condenser unit, first and second steam generators having respective first and second heat exchanger units, and means for circulating a vaporizable motive fiuid through said units in the order named; a gas turbine and an air compressor driven there-by, a gas combustor, and a conduit connected between said combustor and said gas turbine for delivering the combustion products of said combustor to said gas turbine, said compressor discharging oxygen-containing air to said combustor and said steam generators; said steam genera-tors each having a reaction zone for receiving oxygen-containing air from said compressor, means for delivering solid fuel to one region of the reaction zone of said first steam generator so as to be burned therein and to another region of said reaction zone so as to be contacted by the hot products of combustion from said one region whereby combustible make-gas products are generated; said first heat exchange unit being heated by the hot products of combustion of said first steam generator; a first cleaning unit connected to said first steam generator to receive said makegas and including means for separating entrained solid fuel particles from said make-gas, means for delivering said fuel particles from said first cleaning unit to the reaction zone of said second steam generator for admixture with air from said compressor, and means for discharging the cleansed make-gas from said first cleaning unit to said combustor; said second steam generator burning the mixture of air and fuel particles delivered thereto and passing the products of combustion into contact with said second heat exchanger; a second cleaning unit having inlet means arranged to receive the flue gas products of combustion from said second steam generator means for separating out and discharging entrained solid particles, and means for delivering the cleansed flue gas products of combustion from said second cleaning unit to said gas turbine.

9. Power plant apparatus comprising: first and second steam generators, a steam turbine, and means including a parallel flow circuit for conveying a vaporizable motive fluid through said steam generators to said steam turbine; a gas turbine and a gas combustor arranged to discharge its products of combustion to said gas turbine; means for delivering solid fuel to one region of said first steam generator so as to be burned therein and to another region of said reaction zone adjacent said one region so as to be contacted by the hot products of combustion from said one region whereby combustible make-gas products are generated; said motive fluid being heated by the hot products of combustion of said first steam generator; a first cleaning unit adapted to receive make-gas from said first steam generator and including means for separating entrained solid fuel particles from said make-gas, means for delivering said solid particles to said second steam generator, and means for discharging the remaining makegas to said combustor; said second steam generator burning the solid fuel particles delivered thereto and having means for transferring heat from the resultant flue gas to said motive fluid; and a second cleaning unit adapted to receive the flue gas from said second steam generator, said second cleaning unit having means for separating out and discharging entrained solid particles and means for conveying the cleansed flue gas to said gas turbine.

10. Power plant apparatus comprising: a steam turbine, first and second steam generators having respective first and second heat exchanger units in operative association therewith, and means for circulating a vaporizable motive fluid through said units in parallel flow paths, a gas turbine having inlet means and a gas combustor having outlet means connected to the inlet means of said gas turbine, first means for delivering solid fuel to one region of said first steam generator so as to be burned therein, and second means for delivering solid fuel to another region of said reaction zone adjacent said one region so as to be contacted by the hot products of combustion from said one region whereby combustible make-gas products are generated; said first heat exchanger unit being heated by the hot products of combustion of said first steam generator; a first cleaning unit having an inlet connected to said firs-t steam generator so as to receive make-gas from said first steam generator and including means for separating entrained solid fuel particles from said makegas, means for delivering said solid fuel particles to said second steam generator, and means for discharging the remaining make-gas to said combustor; said second steam generator being adapted to burn the solid fuel particles delivered thereto and having means for conveying the resultant flue gas into contact with said second heat exchanger; a second cleaning unit arranged to receive the flue gas from said second steam genera-tor, said second cleaning unit having means for separating out and discharging en-trained solid particles and means for delivering said flue gas after cleaning to said gas turbine.

References Cited by the Examiner UNITED STATES PATENTS 2,500,925 3/1950 Bonvillian 1'1028 2,903,980 9/1959 Gorin 11028 X 3,002,347 10/1961 Sprague 60'39.18 X

FOREIGN PATENTS 597,579 5/1960 Canada.

MARK NEWMAN, Primary Examiner. 

1. THE COMBINATION OF FIRST AND SECOND STEAM GENERATORS, MEANS FOR DELIVERING A VAPORIZABLE FLUID TO SAID STEAM GENERATORS; SAID FIRST STEAM GENERATOR BEING ADAPTED TO BURN FUEL THEREIN SO AS TO GENERATE COMBUSTIBLE MAKEGAS PRODUCTS AND ALSO TO HEAT SAID FLUID; A FIRST GAS CLEANING UNIT CONNECTED TO SAID FIRST STEAM GENERATOR SO AS TO RECEIVE SAID MAKE-GAS, SAID FIRST CLEANING UNIT HAVING MEANS FOR SEPARATING ENTRAINED SOLID PARTICLES FROM SAID MAKE-GAS AND MEANS FOR CONDUCTING SAID PARTICLES TO SAID SECOND STEAM GENERATOR; SAID SECOND STEAM GENERATOR BEING ADAPTED TO BURN THE PARTICLES DELIVERED THERETO FROM SAID FIRST CLEANING UNIT AND HAVING MEANS FOR TRANSFERRING HEAT FROM THE RESULTANT FLUE GAS TO SAID FLUID; A SECOND GAS CLEANING UNIT HAVING INLET MEANS CONNECTED TO SAID SECOND STEAM GENERATOR FOR RECEIVING FLUE GAS AND HAVING MEANS FOR SEPARATING OUT SOLID PARTICLES FROM SAID FLUE GAS; STEAM UTILIZING APPARATUS AND MEANS FOR CONVEYING STEAM THERETO FROM SAID STEAM GENERATORS; GAS UTILIZING APPARATUS, MEANS FOR CONVEYING CLEANSED FLUE GAS THERETO FROM SAID SECOND CLEANING UNIT, A COMBUSTION CHAMBER, MEANS FOR CONVEYING CLEANSED MAKEGAS THERETO FROM SAID FIRST CLEANING UNIT, AND MEANS FOR CONVEYING GAS FROM SAID COMBUSTION CHAMBER TO SAID GAS UTILIZING APPARATUS. 